"These two students are brothers."
Translation:שני התלמידים האלה הם אחים.
Because the verb "to be" has no present tense in hebrew, it is often translated as a copula (in this example, הם). A copula is optional but should be used when it makes a sentence easier to understand. A copula can be used before a noun phrase so that the sentence doesn't sound like the start of a list of noun phrases. A copula can be used before an adjective that could also be a verb so that you know it's not a verb. Don't use a copula before a verb.